With the development of computer, communication and network technology, the progress of global informationization is speeding up. Up to now, network information system has become an infrastructure for countries, industries, groups and enterprises under development. The communication security of the network information system has therefore become an important issue associated with the continuous and stable development of economy and the safety of a country.
At present, chaos has been applied in the secure communication field. The so-called chaos refers to a complex external manifestation resulted from its internal randomicity. In other words, the chaos is a kind of non-random movements that appears to be random. The chaotic signals are characterized by ergodicity, wideband, noise like, sensitive to the initial conditions, rapidly attenuated self correlation and weak cross correlation, and the like. These characteristics provide numerous mechanisms and methods to achieve secure communication. The Chaotic Encryption System in the art includes digital chaotic system and continuous (or analog) chaotic system.
The digital chaotic system is less affected by noise interference and device parameters, and thereby it is easy to run stably for a long time and may be duplicated accurately. However, because digital chaotic sequences are all generated on computers or other equipment with limited precision, any digital chaotic sequence generator may be classified into a finite automation. In this case, the generated digital chaotic sequence presents degraded characteristics, such as short period, strong correlation and small linear complexity; in other words, the dynamics characteristics of a real digital chaotic system are much different from those of ideal real-value chaotic system.
Compared with the digital chaotic system, the continuous chaotic system (i.e. analog chaotic system) has a continuous state (for example, voltage, current etc.) space, which allows the generated chaotic sequences to have a good cryptology characteristic. However, due to the effects of the deviation of device parameters and the circuit noise, it is hard to achieve a stable synchronization between two continuous chaotic systems for a long time. This severely slows the progress of practical application of the chaotic synchronization based secure communication system.